Contents lists available at ScienceDirect Engineering Structures journal homepage: www.elsevier.com/locate/engstruct Review article Eccentric-wing flutter stabilizer for bridges – Analysis, tests, design, and costs U. Starossek ⁎ , T. Ferenczi, J. Priebe Hamburg University of Technology, Denickestr. 17, 21073 Hamburg, Germany ARTICLE INFO Keywords: Passive aerodynamic damper Fixed wing Flutter analysis Wind tunnel test Design study Cost estimate ABSTRACT A device is presented that aims at preventing bridge flutter. It consists of wings positioned along the sides of, and fixed to, the bridge deck. Flutter suppression effectiveness is high provided the lateral eccentricity of the wings is large. It is a passive aerodynamic device that is presumably more cost-efficient than other passive measures or devices. Moreover, it does not contain moving parts. This is an advantage over devices with moving parts, which meet resistance due to reliability and durability concerns. Wind-tunnel tests were performed in which the flutter speed of a bridge deck sectional model without wings and with wings mounted in various configurations was measured. The experimental results are presented and compared with the results of flutter analyses using finite aeroelastic beam elements. Using the analytical approach, also the effect of the distribution of the wings along the length of a bridge was studied to optimize this distribution. Preliminary design studies for the wings and their support structures as well as quantity and cost estimates are presented. For a representative example bridge and wing configuration, an increase of 22% of flutter speed is reached at a cost increase of 2.5%. 1. Introduction Flutter is a phenomenon that governs the design of long-span bridges. Various measures have been proposed and applied to raise the flutter resistance of bridges, that is, their critical wind speed for flutter onset (flutter speed). The concept of the twin suspension bridge was described by Richardson [1] and since implemented in a few bridges. It is a passive aerodynamic measure that takes advantage of the gap between the two (or more) bridge decks. The flutter speed increase thus achieved comes at the additional cost of the cross beams that are needed to connect the individual decks. An active aerodynamic device for raising the flutter speed was proposed by Ostenfeld and Larsen [2]. It consists of wings, installed along the sides of the bridge deck, whose pitch is controlled by actua- tors. A closed-loop control is envisaged in which, based on accel- erometer measurements, an algorithm produces the control signals for the actuators such that the movement of the wings generate stabilizing wind forces. With such device, the safety of the bridge depends on energy supply and the proper functioning of control software and hardware – a condition that meets resistance with bridge owners and authorities due to reliability and durability concerns. A passive aero- dynamic-mechanical device described by Starossek and Aslan [3] also includes variable-pitch wings along the sides of the bridge deck. Instead of being controlled by actuators, the pitch of the wings follows the movements of tuned mass dampers inside the bridge deck to which the wings are coupled by means of linkages or gears. With proper tuning, the flutter suppression effectiveness can be similar to that of actively controlled wings. Being a passive device, the safety of the bridge would not depend on energy supply and a control system. It still includes moving parts though, which raises the threshold of acceptance. Diana et al. [4] examined the effect of various aerodynamic devices rigidly attached to the deck of the envisaged Messina Strait Bridge, including winglets positioned along the edges of the deck. The devices are positioned close to the deck without a distinct vertical or horizontal offset. Hence they form part of the aerodynamic contour of the deck and influence the flow field around it. Only qualitative indications are given in [4] concerning the impact of such devices on the flutter behavior of the bridge and it does not become clear whether and by how much the flutter speed is raised by the examined winglets. Raggett [5] suggested a pair of wings rigidly mounted above, or slightly outboard of, the two edges of the bridge deck to stabilize the bridge against flutter. The wings are arranged with a distinct vertical offset from the deck so that they are aerodynamically independent of the deck. Liu et al. [6] considered a similar configuration and studied its influence on bridge flutter both analytically and by sectional model wind tunnel tests. When the wings are considered aerodynamically independent of the deck, their impact on the flutter speed of the bridge https://doi.org/10.1016/j.engstruct.2018.06.056 ⁎ Corresponding author. E-mail address: starossek@tuhh.de (U. Starossek). Engineering Structures 172 (2018) 1073–1080 0141-0296/ © 2018 Elsevier Ltd. All rights reserved. T